In a low point for the former Knick coach, Pitino was forced yesterday to recount in graphic detail his “15-second” sexual encounter with the woman now on trial for allegedly extorting him.

Under cross-examination, he said he did not use a condom when he had sex with Karen Cunagin Sypher in 2003.

“She said to me that she is extremely fertile. She said her husband had looked at her four times and that she got pregnant.”

Then Pitino said he “immediately pulled out.”

Sypher, who became pregnant and had an abortion, is accused of threatening to reveal their encounter if the University of Louisville head coach did not pay her.

Despite his buzzer-beating maneuver, Pitino added that “it is physically possible” that the baby was his.

Worried that his wife and kids would find out he had a one-night stand with a woman he’d met in a restaurant, Pitino acknowledged that he didn’t immediately tell police about demands for cars, cash and housing, in order to keep the tryst secret.

The basketball coach told jurors he kept quiet for nearly two months, hoping he could “contain” the damaging information.

Pitino and defense attorney James Earhart frequently cut each other off during questioning, and the tension escalated as Earhart pushed Pitino to address Sypher’s rape allegations.

Pitino interrupted, saying he was “here to give the truth.” Earhart retorted, “I bet you are.”

“I don’t fear the truth,” Pitino said.

“Neither do we,” Earhart shot back.

He said that one of the biggest disappointments was that the incident caused an end to his working relationship with his son, Richard, an assistant coach on his staff.

When Pitino’s testimony ended, he had spent about six hours on the witness stand.

Sypher, 50, has pleaded not guilty. She filed a rape report with police after she was indicted last year, about six years after she and Pitino, 57, had sex in an empty restaurant a few hours after they’d met. Authorities have said her rape claim lacks merit, and no charges were filed.